0

I want to change the Coordinate Reference System of some raster and vector layers which are from different types and origins so that all are in the same CRS. In QGIS when I want to change the CRS of the project, several transformation options are available for each CRS. I have expanded my question, giving better context and details, here:

R Terra package, project: changing the coordinate reference system specifying the transformation type

Andres
  • 59
  • 6
  • 1
    Yes? Maybe? It's hard to guess what you might need to be worried about. A [reproducible example](https://stackoverflow.com/q/5963269/5325862) would help, but how you deal with CRS depends on what you're trying to do and why – camille Apr 12 '23 at 17:21
  • Thanks camille, I added more context and details in my post. – Andres Apr 23 '23 at 10:17

1 Answers1

1

I'm familiar with what you're talking about from ArcGIS. I'm not sure the reason why this is different, but I've never seen this in R I don't think you need to worry about it.

I do this all the time. This is the workflow I use.

First, I define the CRS that I'm planning to use for many different rasters early on in my workflow.

LCC <- "+init=EPSG:3347"

WGS84 <- "+init=EPSG:4326"

NAD83 <- "+init=EPSG:4269"

WClim_CRS <- "GEOGCRS[\"WGS 84\",\n    DATUM[\"World Geodetic System 1984\",\n        ELLIPSOID[\"WGS 84\",6378137,298.257223563,\n            LENGTHUNIT[\"metre\",1]]],\n    PRIMEM[\"Greenwich\",0,\n        ANGLEUNIT[\"degree\",0.0174532925199433]],\n    CS[ellipsoidal,2],\n        AXIS[\"geodetic latitude (Lat)\",north,\n            ORDER[1],\n            ANGLEUNIT[\"degree\",0.0174532925199433]],\n        AXIS[\"geodetic longitude (Lon)\",east,\n            ORDER[2],\n            ANGLEUNIT[\"degree\",0.0174532925199433]],\n    ID[\"EPSG\",4326]]"

Then later in my workflow, whenever I want to transform a raster to have the same CRS as the rest, I use these pre-defined CRS objects

remove_area <- terra::project(remove_area, LCC)

nfld <- terra::project(nfld, LCC)

bioclim_ssp245_can  <- terra::project(bioclim_ssp245_can, LCC)
bioclim_ssp585_can  <- terra::project(bioclim_ssp585_can , LCC)
canderson156
  • 1,045
  • 10
  • 24
  • Thank you very much @canderson156. I also have good results, of that's what I think, just using the 'project' function without worrying about the different transformation options that QGIS provides. Anyway, I added more context and details in my post, I still would like to know the reason why QGIS forces the user to choose a transformation type. – Andres Apr 23 '23 at 10:24